Re: [PATCH 5/5] arm: kexec_file: load zImage or uImage, initrd and dtb

From: Lukasz Stelmach <l.stelmach@samsung.com>
To: Russell King - ARM Linux admin <linux@armlinux.org.uk>
Cc: Masahiro Yamada <masahiroy@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Enrico Weigelt <info@metux.net>,
	Kees Cook <keescook@chromium.org>, Ingo Molnar <mingo@kernel.org>,
	Ben Dooks <ben-linux@fluff.org>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org,
	AKASHI Takahiro <takahiro.akashi@linaro.org>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
	Marek Szyprowski <m.szyprowski@samsung.com>
Subject: Re: [PATCH 5/5] arm: kexec_file: load zImage or uImage, initrd and dtb
Date: Mon, 01 Jun 2020 20:48:08 +0200	[thread overview]
Message-ID: <dleftjeeqysjvb.fsf%l.stelmach@samsung.com> (raw)
In-Reply-To: <20200601150745.GL1551@shell.armlinux.org.uk> (Russell King's message of "Mon, 1 Jun 2020 16:07:45 +0100")

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It was <2020-06-01 pon 16:07>, when Russell King - ARM Linux admin wrote:
> On Mon, Jun 01, 2020 at 04:27:54PM +0200, Łukasz Stelmach wrote:
>> This is kexec_file_load implementation for ARM. It loads zImage and
>> initrd from file descripters and resuses DTB.
>> 
>> Most code is derived from arm64 kexec_file_load implementation
>> and from kexec-tools.
>
> Please make the uImage loader able to be configured out of the
> kernel; it's a legacy image format now, and some of us just don't
> use it anymore.  That way, those who wish to have it can, and
> those who wish not to can have a smaller kernel.

The difference in size of arch/arm/boot/Image is 160 bytes, but
OK. Done.

>> Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>
>> Signed-off-by: Łukasz Stelmach <l.stelmach@samsung.com>
>> ---
>>  arch/arm/Kconfig                     |  15 ++
>>  arch/arm/include/asm/image.h         |  26 ++++
>>  arch/arm/include/asm/kexec.h         |  14 ++
>>  arch/arm/kernel/Makefile             |   5 +-
>>  arch/arm/kernel/kexec_uimage.c       |  80 ++++++++++
>>  arch/arm/kernel/kexec_zimage.c       | 199 +++++++++++++++++++++++++
>>  arch/arm/kernel/machine_kexec.c      |  11 +-
>>  arch/arm/kernel/machine_kexec_file.c | 209 +++++++++++++++++++++++++++
>>  8 files changed, 554 insertions(+), 5 deletions(-)
>>  create mode 100644 arch/arm/kernel/kexec_uimage.c
>>  create mode 100644 arch/arm/kernel/kexec_zimage.c
>>  create mode 100644 arch/arm/kernel/machine_kexec_file.c
>> 
>> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
>> index c77c93c485a0..6adb849cb304 100644
>> --- a/arch/arm/Kconfig
>> +++ b/arch/arm/Kconfig
>> @@ -1917,6 +1917,21 @@ config KEXEC
>>  	  is properly shutdown, so do not be surprised if this code does not
>>  	  initially work for you.
>>  
>> +config KEXEC_FILE
>> +	bool "Kexec file based system call (EXPERIMENTAL)"
>> +	depends on (!SMP || PM_SLEEP_SMP)
>> +	depends on USE_OF
>> +	select KEXEC_CORE
>> +	select CRC32
>> +	help
>> +	  This is new version of kexec system call. This system call is
>> +	  file based and takes file descriptors as system call argument
>> +	  for kernel and initramfs as opposed to list of segments as
>> +	  accepted by previous system call.
>> +
>> +	  The kernel to be loaded MUST support Flattened Device Tree
>> +	  (selected with CONFIG_USE_OF).
>> +
>>  config ATAGS_PROC
>>  	bool "Export atags in procfs"
>>  	depends on ATAGS && KEXEC
>> diff --git a/arch/arm/include/asm/image.h b/arch/arm/include/asm/image.h
>> index 624438740f23..95f23837b04f 100644
>> --- a/arch/arm/include/asm/image.h
>> +++ b/arch/arm/include/asm/image.h
>> @@ -8,8 +8,13 @@
>>  			 (((x) >>  8) & 0x0000ff00) |  \
>>  			 (((x) <<  8) & 0x00ff0000) |  \
>>  			 (((x) << 24) & 0xff000000))
>> +#define UIMAGE_MAGIC(x) (x)
>>  #else
>>  #define ZIMAGE_MAGIC(x) (x)
>> +#define UIMAGE_MAGIC(x) ((((x) >> 24) & 0x000000ff) | \
>> +			 (((x) >>  8) & 0x0000ff00) |  \
>> +			 (((x) <<  8) & 0x00ff0000) |  \
>> +			 (((x) << 24) & 0xff000000))
>>  #endif
>>  
>>  #define ARM_ZIMAGE_MAGIC1 ZIMAGE_MAGIC(0x016f2818)
>> @@ -17,6 +22,12 @@
>>  #define ARM_ZIMAGE_MAGIC3 ZIMAGE_MAGIC(0x5a534c4b)
>>  #define ARM_ZIMAGE_MAGIC4 ZIMAGE_MAGIC(0x5a534344)
>>  
>> +#define ARM_UIMAGE_MAGIC UIMAGE_MAGIC(0x27051956)
>> +#define ARM_UIMAGE_NAME_LEN		32
>> +#define ARM_UIMAGE_TYPE_KERNEL		2
>> +#define ARM_UIMAGE_TYPE_KERNEL_NOLOAD	14
>> +#define ARM_UIMAGE_ARCH_ARM		2
>> +
>>  #ifndef __ASSEMBLY__
>>  
>>  #include <linux/types.h>
>> @@ -33,6 +44,21 @@ struct arm_zimage_header {
>>  	__le32 extension_tag_offset;
>>  };
>>  
>> +struct arm_uimage_header {
>> +	__be32 magic;
>> +	__be32 hdr_crc;
>> +	__be32 time;
>> +	__be32 size;
>> +	__be32 load;
>> +	__be32 entry;
>> +	__be32 crc;
>> +	__u8   os;
>> +	__u8   arch;
>> +	__u8   type;
>> +	__u8   comp;
>> +	__u8   name[ARM_UIMAGE_NAME_LEN];
>> +};
>> +
>>  struct arm_zimage_tag {
>>  	struct tag_header hdr;
>>  	union {
>> diff --git a/arch/arm/include/asm/kexec.h b/arch/arm/include/asm/kexec.h
>> index 22751b5b5735..fda35afa7195 100644
>> --- a/arch/arm/include/asm/kexec.h
>> +++ b/arch/arm/include/asm/kexec.h
>> @@ -83,6 +83,20 @@ static inline struct page *boot_pfn_to_page(unsigned long boot_pfn)
>>  }
>>  #define boot_pfn_to_page boot_pfn_to_page
>>  
>> +#ifdef CONFIG_KEXEC_FILE
>> +
>> +extern const struct kexec_file_ops kexec_zimage_ops;
>> +extern const struct kexec_file_ops kexec_uimage_ops;
>> +
>> +struct kimage;
>> +
>> +extern int load_other_segments(struct kimage *image,
>> +		unsigned long kernel_load_addr, unsigned long kernel_size,
>> +		char *initrd, unsigned long initrd_len,
>> +		unsigned long initrd_offset, char *cmdline);
>> +
>> +#endif /* CONFIG_KEXEC_FILE */
>> +
>>  #endif /* __ASSEMBLY__ */
>>  
>>  #endif /* CONFIG_KEXEC */
>> diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
>> index 89e5d864e923..466c683bb551 100644
>> --- a/arch/arm/kernel/Makefile
>> +++ b/arch/arm/kernel/Makefile
>> @@ -3,6 +3,7 @@
>>  # Makefile for the linux kernel.
>>  #
>>  
>> +CFLAGS_kexec_zimage.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
>>  CPPFLAGS_vmlinux.lds := -DTEXT_OFFSET=$(TEXT_OFFSET)
>>  AFLAGS_head.o        := -DTEXT_OFFSET=$(TEXT_OFFSET)
>>  
>> @@ -56,7 +57,9 @@ obj-$(CONFIG_FUNCTION_TRACER)	+= entry-ftrace.o
>>  obj-$(CONFIG_DYNAMIC_FTRACE)	+= ftrace.o insn.o patch.o
>>  obj-$(CONFIG_FUNCTION_GRAPH_TRACER)	+= ftrace.o insn.o patch.o
>>  obj-$(CONFIG_JUMP_LABEL)	+= jump_label.o insn.o patch.o
>> -obj-$(CONFIG_KEXEC)		+= machine_kexec.o relocate_kernel.o
>> +obj-$(CONFIG_KEXEC_CORE)	+= machine_kexec.o relocate_kernel.o
>> +obj-$(CONFIG_KEXEC_FILE)	+= machine_kexec_file.o kexec_zimage.o	\
>> +				   kexec_uimage.o
>>  # Main staffs in KPROBES are in arch/arm/probes/ .
>>  obj-$(CONFIG_KPROBES)		+= patch.o insn.o
>>  obj-$(CONFIG_OABI_COMPAT)	+= sys_oabi-compat.o
>> diff --git a/arch/arm/kernel/kexec_uimage.c b/arch/arm/kernel/kexec_uimage.c
>> new file mode 100644
>> index 000000000000..47033574e24e
>> --- /dev/null
>> +++ b/arch/arm/kernel/kexec_uimage.c
>> @@ -0,0 +1,80 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Kexec uImage loader
>> + *
>> + * Copyright (C) 2020 Samsung Electronics
>> + * Author: Łukasz Stelmach <l.stelmach@samsung.com>
>> + */
>> +
>> +#define pr_fmt(fmt)	"kexec_file(uImage): " fmt
>> +
>> +#include <asm/image.h>
>> +#include <linux/crc32.h>
>> +#include <linux/err.h>
>> +#include <linux/kexec.h>
>> +
>> +#define crc32_ones(crc, buf, len) \
>> +	(crc32(crc ^ 0xffffffff, buf, len) ^ 0xffffffff)
>> +
>> +static int uimage_probe(const char *uimage_buf, unsigned long uimage_len)
>> +{
>> +	const struct arm_uimage_header *h =
>> +		(struct arm_uimage_header *) uimage_buf;
>> +	struct arm_uimage_header uhdr;
>> +	unsigned long zoff = sizeof(struct arm_uimage_header);
>> +	uint32_t crc;
>> +
>> +	if (h->magic != ARM_UIMAGE_MAGIC)
>> +		return -EINVAL;
>> +
>> +	if (h->type != ARM_UIMAGE_TYPE_KERNEL &&
>> +	    h->type != ARM_UIMAGE_TYPE_KERNEL_NOLOAD){
>> +		pr_debug("Invalid image type: %d\n", h->type);
>> +		return -EINVAL;
>> +	}
>> +
>> +	if (h->arch != ARM_UIMAGE_ARCH_ARM) {
>> +		pr_debug("Invalidy image arch: %d\n", h->arch);
>> +		return -EINVAL;
>> +	}
>> +
>> +	memcpy((char *)&uhdr, h, sizeof(uhdr));
>> +	crc = be32_to_cpu(uhdr.hdr_crc);
>> +	uhdr.hdr_crc = 0;
>> +
>> +	if (crc32_ones(0, (char *)&uhdr, sizeof(uhdr)) != crc) {
>> +		pr_debug("Corrupt header, CRC do not match\n");
>> +		return -EINVAL;
>> +	}
>> +
>> +	crc = be32_to_cpu(uhdr.crc);
>> +	if (crc32_ones(0, uimage_buf + zoff, uimage_len - zoff) != crc) {
>> +		pr_debug("Corrupt zImage, CRC do not match\n");
>> +		return -EINVAL;
>> +	}
>> +
>> +	return kexec_zimage_ops.probe(uimage_buf + zoff,
>> +				      uimage_len - zoff);
>> +}
>> +
>> +static void *uimage_load(struct kimage *image,
>> +				char *uimage, unsigned long uimage_len,
>> +				char *initrd, unsigned long initrd_len,
>> +				char *cmdline, unsigned long cmdline_len)
>> +{
>> +	const struct arm_uimage_header *h =
>> +		(struct arm_uimage_header *) uimage;
>> +	unsigned long zimage_offset = sizeof(struct arm_uimage_header);
>> +
>> +	pr_debug("Loading uImage");
>> +	return kexec_zimage_ops.load(image,
>> +				     uimage + zimage_offset,
>> +				     uimage_len - zimage_offset,
>> +				     initrd, initrd_len,
>> +				     cmdline, cmdline_len);
>> +}
>> +
>> +const struct kexec_file_ops kexec_uimage_ops = {
>> +	.probe = uimage_probe,
>> +	.load = uimage_load,
>> +};
>> diff --git a/arch/arm/kernel/kexec_zimage.c b/arch/arm/kernel/kexec_zimage.c
>> new file mode 100644
>> index 000000000000..d09795fc9072
>> --- /dev/null
>> +++ b/arch/arm/kernel/kexec_zimage.c
>> @@ -0,0 +1,199 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Kexec zImage loader
>> + *
>> + * Copyright (C) 2020 Samsung Electronics
>> + * Author: Łukasz Stelmach <l.stelmach@samsung.com>
>
> Please credit me as part author of this - you have taken some of my
> code from the userspace kexec tool (such as the contents of
> find_extension_tag()) and copied it in here, so this is not all your
> own work.

Done.

>> + */
>> +
>> +#define pr_fmt(fmt)	"kexec_file(zImage): " fmt
>> +
>> +#include <asm/image.h>
>> +#include <asm/unaligned.h>
>> +#include <linux/err.h>
>> +#include <linux/kexec.h>
>> +#include <linux/memblock.h>
>> +
>> +#define byte_size(t)    ((t)->hdr.size << 2)
>> +
>> +static const void *find_extension_tag(const char *buf,
>> +						       unsigned long len,
>> +						       uint32_t tag_id)
>> +{
>> +	const struct arm_zimage_header *h = (const struct arm_zimage_header *)buf;
>> +	const struct arm_zimage_tag *tag;
>> +	uint32_t offset, size;
>> +	uint32_t max = len - sizeof(struct tag_header);
>> +
>> +	if (len < sizeof(*h) ||
>> +	    h->magic != ARM_ZIMAGE_MAGIC1 ||
>> +	    h->magic2 != ARM_ZIMAGE_MAGIC2)
>> +		return NULL;
>> +
>> +	for (offset = h->extension_tag_offset;
>> +	     (tag = (void *)(buf + offset)) != NULL &&
>> +		     offset < max &&
>> +		     (size = le32_to_cpu(byte_size(tag))) != 0 &&
>> +		     offset + size < len;
>> +	     offset += size) {
>> +		pr_debug("  offset 0x%08x tag 0x%08x size %u\n",
>> +			  offset, le32_to_cpu(tag->hdr.tag), size);
>> +		if (tag->hdr.tag == tag_id)
>> +			return tag;
>> +	}
>> +
>> +	return NULL;
>> +}
>> +
>> +static int zimage_probe(const char *kernel_buf, unsigned long kernel_len)
>> +{
>> +	const struct arm_zimage_header *h =
>> +		(struct arm_zimage_header *)(kernel_buf);
>> +
>> +	if (!h || (kernel_len < sizeof(*h)))
>> +		return -EINVAL;
>> +
>> +	if ((h->magic != ARM_ZIMAGE_MAGIC1) ||
>> +	    (h->magic2 != ARM_ZIMAGE_MAGIC2))
>> +		return -EINVAL;
>> +
>> +	return 0;
>> +}
>> +
>> +
>> +#if defined(DEBUG)
>> +#define debug_offsets() ({			\
>> +	pr_debug("Image offsets:\n");		\
>> +	pr_debug("  kernel 0x%08lx 0x%08lx\n", kernel_offset, kernel_len); \
>> +	pr_debug("  zimage 0x%08lx 0x%08lx\n", zimage_offset, zimage_len); \
>> +	pr_debug("  initrd 0x%08lx 0x%08lx\n", initrd_offset, initrd_len); \
>> +})
>> +#else
>> +#define debug_offsets()
>> +#endif
>> +
>> +static void *zimage_load(struct kimage *image,
>> +				char *zimage, unsigned long zimage_len,
>> +				char *initrd, unsigned long initrd_len,
>> +				char *cmdline, unsigned long cmdline_len)
>> +{
>> +	struct arm_zimage_header *h;
>> +	struct kexec_buf kbuf;
>> +	struct kexec_segment *zimage_segment;
>> +	const struct arm_zimage_tag *klsz_tag;
>> +	const struct arm_zimage_tag_dc *dcsz_tag;
>> +	int ret = -EINVAL;
>> +
>> +	unsigned long zimage_mem = 0x20000; /* malloc 64kB + stack 4 kB + some bss */
>> +	unsigned long kernel_len = zimage_len * 4; /* 4:1 compression */
>
> This has been proven wrong.

5:1? The comment and the code in kexec-tools are inconsisten in this
regard. The comment says 4:1, but the code multiplies by 5. Your
recommendation? This value is used as a fallback anyway in a very
unlikely case, when tags are missing (see below).

>> +	unsigned long kernel_offset = memblock_start_of_DRAM() +
>> +		ALIGN(TEXT_OFFSET, PAGE_SIZE);
>
> TEXT_OFFSET is actually a property of the loaded kernel, not of the
> currently running kernel.

Indeed.

> I have a patch to add that into the zImage tag.

I am afraid, I haven't seen it before. Where can I find it?

>> +	unsigned long zimage_offset = kernel_offset +
>> +		ALIGN(kernel_len, PAGE_SIZE);
>> +	unsigned long initrd_offset = zimage_offset +
>> +		ALIGN(zimage_len + zimage_mem, PAGE_SIZE);
>
> Since kernel_len is wrong, these will be wrong... please only fall
> back to this if you don't find the extension tag - in other words,
> declare the variables here, but don't initialise them, set them
> lower down in the file if we fail to find the extension tag.

That is how it works now. This is the structure I have taken from
kexec-tools: initialize and change if additional information is
available. If the tags are not available use these values as a fallback.

>> +
>> +	if (image->type == KEXEC_TYPE_CRASH) {
>> +		kernel_offset += crashk_res.start;
>> +		zimage_offset += crashk_res.start;
>> +		initrd_offset += crashk_res.start;
>> +	}
>> +	debug_offsets();
>> +
>> +	h = (struct arm_zimage_header *)zimage;
>> +
>> +	klsz_tag = find_extension_tag(zimage, zimage_len, ZIMAGE_TAG_KRNL_SIZE);
>> +	if (klsz_tag) {
>> +		uint32_t *p = (void *)zimage +
>> +			le32_to_cpu(klsz_tag->u.krnl_size.size_ptr);
>> +		uint32_t edata_size = le32_to_cpu(get_unaligned(p));
>> +		uint32_t bss_size = le32_to_cpu(klsz_tag->u.krnl_size.bss_size);
>> +
>> +		kernel_len = edata_size + bss_size;
>> +
>> +		pr_debug("Decompressed kernel sizes:\n");
>> +		pr_debug(" text+data 0x%08lx bss 0x%08lx total 0x%08lx\n",
>> +			 (unsigned long)edata_size,
>> +			 (unsigned long)bss_size,
>> +			 (unsigned long)kernel_len);
>> +
>> +		zimage_offset = kernel_offset + ALIGN(edata_size, PAGE_SIZE);
>> +		initrd_offset = zimage_offset +
>> +			max(ALIGN(zimage_len + 0x20000, PAGE_SIZE),
>> +			    ALIGN((unsigned long)bss_size, PAGE_SIZE));
>> +		debug_offsets();
>
> This looks incorrect to me.  Please see the kexec tool - what its doing
> in its corresponding section that you copied some of this code from is
> carefully thought out and can't be simplified.  Ergo, I think this is
> wrong.

As I explained in <dleftjwo4qsqqf.fsf%l.stelmach@samsung.com> my
approach is slightly different. I am trying to avoid copying zImage by
putting it hight enough in the first place.

Kind regards,
-- 
Łukasz Stelmach
Samsung R&D Institute Poland
Samsung Electronics

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